The invention relates to video switchers and video digital effects apparatus, and particularly to a digital video effects unit integrally inserted within various internal paths of a video switcher apparatus.
Within the past few years, the use of digital effects to manipulate video signals has increased dramatically in the field of television, and has resulted in a myriad of special effects which, in turn, are of particular interest to television broadcasting facilities and video post production studios. Since switchers have long been used for generating analog effects and otherwise manipulating video signals, it follows that the desirability for supplying digital special effects via a video switcher also has increased dramatically.
In response to this need, digital effects interfaces have been developed which allow coupling a digital effects unit to a video switcher to supply various digital special effects via the switcher. However, such digital effects/video switcher interfaces presently available have limited capabilities. To illustrate, video switcher architectures require a switching matrix for supplying video source signals to a multichannel effects processor (mixer) and key source signals to a key processor (keyer) circuitry. The keyer output then is fed to the mixer, which combines the various video source signals using the key hole cutting signals supplied by the keyer, as well as bus transition boundary signals provided by a pattern generating circuit. As part of the interface, the digital effects unit is fed from auxiliary buses, and the outputs therefrom are supplied as input video and external key sources to the switcher. These signals then are combined by the switcher in conventional fashion with keying done on the output of the digital effects unit.
As may be seen, digital effects interfaces thus are merely a patchwork solution to an existing problem, and one which fails to take advantage of the potential value of integrally combining the preferred features of the two systems. For example, a digital effects device is not a video source such as, for example, video cameras, video tape recorders, test pattern generators, character generators, etc., which normally comprise the video sources which supply a video switcher via its main input matrix. Yet, in the patchwork interface solution, the digital effects device is employed as a video source whose manipulated video output is supplied to the switcher main input matrix. This is an inefficient configuration.
Other video signal handling apparatus include, for example, a video digital effects system having a video input switching device for supplying video and key signals to a signal transforming unit. The resulting transformed signals are supplied to an adder to be combined into a video signal which has been compressed, expanded, rotated or otherwise moved about a television raster. Although such a digital effects system is capable of extensive video signal manipulation, it does not provide the functions of a switcher apparatus. Furthermore, in practical video broadcast facilities and post production studios, the transformed signals generated by such a digital effects system thereafter generally are supplied to a switcher apparatus for further manipulation such as, for example, signal mixing. Since the digital effects unit also provides a signal mixing process, the patchwork interface solution repeates the process twice needlessly.
Accordingly, it would be highly desirable to combine a digital effects unit as an integral part of a video switcher, whereby features of one system are integrally shared and utilized by the other system to provide a relatively powerful switcher apparatus. That is, it would be preferable to use a digital effects unit as a video manipulating device much in the manner of a keyer or a mixer within the switcher, rather than as a video source.
To this end, in accordance with the invention, the switcher internal paths corresponding to the video source signals and the control signals extending to the mixer, are interrupted, and a digital effects unit is, in effect, inserted in the paths. Such an integral configuration provides switcher operation enhanced by the digital effects unit to provide special effects heretofore unavailable, or available only by patching components together, when using the digital effects interface of previous mention. In the present invention, an operator may perform switcher transitions and effects via conventional switcher control inputs, with the digital effects appearing as additions to the switcher operations. Signal sources for the digital effects unit now effectively are provided internally by the switcher, and the digital effects unit outputs are reinserted directly back into the switcher as video source and control signals for the mixer within the switcher. As a result, the digital effects unit is invisible to an operator; that is, the digital effects generated appear as modifications to the basic switcher functions of digital wipes, key processing, external key inputs, analog pattern key hole cutting, etc.
Preferably, the source video and key signal paths, or buses, from the input matrix, keyer and pattern generator, which extend to the mixer within the switcher, are made interruptible via respective cross-points and connecting lines arranged to re-route the paths, thereby defining an internally "inserted" digital effects, or switching, loop means. Selectively manipulating a selected crosspoint, or crosspoints, allows the corresponding switcher signals to be redirected to dedicated digital effects input buses coupled to the digital effects unit. The resulting digital effects signals, such as transformed video and key signals, then are supplied via dedicated digital effects output buses back to the continuation of the interrupted paths, to thus provide the inputs to the mixer. The various crosspoints, the connecting lines and the dedicated input and ouput digital effects buses together define the internally combined digital effects loop within the switcher apparatus. The paths through the digital effects unit have a delay of two fields, but will look like zero time to the switcher. Thus the digital effects unit is used as a switcher internal signal manipulating device, not as an input video or external key source as in the present patchwork interface configurations. As a result, the switcher may efficiently supply digital effects which appear as additions to conventional switcher transition and effect operations, without requiring additional input from an operator.
As may be seen, the invention contemplates use with a digital video switcher as well as with the analog video switcher described herein by way of example only.